Below is the program I've written to find the exponent of 6, but I this its giving wrong output or I may be wrong somewhere, I'm unable to figure out here.
#include<bits/stdc++.h>
using namespace std;
#define ll long long
int main()
{
ll t;
cin>>t;
cout<<log(t)/log(6)<<"\n";
cout<<floor(log(t)/log(6))<<"\n";
cout<<ceil(log(t)/log(6));
return 0;
}
Input:-
216
Output:-
3
3
4
Since 216 can be written as 6*6*6, so whether there is ceil or floor the output should be 3 in all three cases.
Answering to my own question, this problem can be solved by setting small precision(here up to 2 decimal digits), below is the program for the same.
#include<bits/stdc++.h>
using namespace std;
int main()
{
int t;
cin>>t;
cout<<log(t)/log(6)<<"\n";
cout<<floor((floor(log(t)/log(6)*100.0)/100.0))<<"\n";
cout<<ceil((floor(log(t)/log(6)*100.0)/100.0));
return 0;
}
The log function - like most floating point calculations - is imprecise. There is often tiny amount of error in the result. In your case, you did not get the exact 3, but some value slightly greater than 3. When you apply ceil or floor to such imprecise result, you may increase or reduce the amount of the error up to a whole number. In this case you increased the error by ceiling the result from nearly correct integer to exactly following integer).